Income Taxes - Schedule of Deferred Income Taxes (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Depreciable assets	$ (905)	$ (1,019)
Deferred revenue	1,554
Accruals and reserves	585	1,308
Stock-based compensation	2,213	1,798
Impaired strategic investments	1,666	1,687
NOL carryforwards	3,308	4,637
U.S. Federal and state R&D credits	2,394	1,896
Other	689	538
Valuation allowance	(5,328)	(4,541)
Total deferred tax assets	$ 6,176	$ 6,304

Deferred tax assets impaired investment.

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Deferred tax assets (liabilities) property plant and equipment.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from in-process research and development costs expensed in connection with a business combination.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards classified as noncurrent.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from reserves and accruals.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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